Production of low molecular weight polyanhydrides and epoxy compositions derived therefrom

ABSTRACT

POLYANHYDRIDES ARE PRODUCED BY A NOVEL BULK POLYMERIZATION PROCEDURE FROM MALEIC MONOMERS AND ALKYL STYRENES. THE POLYANHYDRIDES, OF LOW MOLECULAR WEIGHT AND CONTAINING MALEIC MONOMER TO ALKYL STYRENE IN A RATIO GREATER THAN 1 TO 1, ARE PARTICULARLY USEFUL AS HARDENERS FOR EPOXY RESIN-CONTAINING COMPOSITION AND GIVE RISE TO EPOXY COMPOSITIONS WHICH RESULT IN CURED PRODUCTS EXHIBITING HIGH HEAT DISTORTION TEMPERATURES AND EXCELLENT ELECTRICAL AND SELF LIFE PROPERTIES.

United States Patent Oflice 3,732,332 PRODUCTION OF LOW MOLECULAR WEIGHT POLYANHYDRIDES AND EPOXY COMPOSI- TIONS DERIVED THEREFROM Omer E. Curtis, Jr., Morristown, Harold W. Tuller, Long Valley, Charles T. ONeill, Dover, and Ralph W. Nussbaum, West Orange, N.J., assignors to Allied Chemical Corporation N Drawing. Filed Oct. 16, 1970, Ser. No. 81,616 Int. Cl. C08g 45/04 US. Cl. 260-837 R 16 Claims ABSTRACT OF THE DISCLOSURE Polyanhydrides are produced by a novel bulk polymerization procedure from maleic monomers and alkyl styrenes. The polyanhydrides, of low molecular weight and containing maleic monomer to alkyl styrene in a ratio greater than 1 to l, are particularly useful as hardeners for epoxy resin-containing compositions and give rise to epoxy compositions which result in cured products exhibiting high heat distortion temperatures and excellent electrical and self life properties.

The present invention relates to a novel process for the mass or bulk polymerization of maleic monomers with alkyl substituted vinyl hydrocarbons, to novel products resulting from such a process and to novel epoxy compositions derived therefrom. One specific aspect of the present invention relates to a bulk polymerization process for preparing novel, low molecular weight polymers of a maleic monomer and vinyl aromatic hydrocarbon, typically co-polymers of maleic anhydride and a-methyl styrene which are particularly useful as hardeners in epoxy compositions.

There is growing interest in low molecular weight polymers of maleic monomers, Heretofore, it has been proposed to employ various techniques of solution, bulk and the like procedures to co-polymerize maleic monomers and vinyl hydrocarbons such as styrene. Of the bulk polymerization techniques it has been proposed to copolymerize styrene and maleic anhydride in a 1:1 molar ratio employing a polymerization catalyst wherein the reagents along with the catalyst are mixed together and then heated to polymerization temperatures giving rise to products of very high viscosity and of very high molecular weights.

By far the most common mode of preparing copolymers of maleic monomers and vinyl hydrocarbon employed in the art today are solvent or solution polymerization processes which are relatively costly since they require removal of the large amounts of solvent required and in general only permit 10 to 50 percent utilization of kettle capacity for the actual product being produced.

While low molecular weight copolymers have been prepared, e.g. copolymers of a molecular weight of less than 10,000 generally within the range of 1500 to 2,000, the molecular weight has been subject to the effect of controlling at least three variables with either or all of them exerting adverse effects. For example, it has been widely held heretofore that either of higher temperatures, larger amounts of catalyst or the selection of particular solvents such as xylene would result in copolymers of molecular weights below 10,000 depending on how these parameters were controlled.

Despite the abundant amount of work done in this area, however, there still exists serious disadvantages which preclude successful preparation of low molecular weight products. The prior procedures have suffered from the disadvantages inherent in the facts that control of the polymerization reaction once initiated has been difficult; copolymers produced generally have a broad molecular Weight range and, in general, only high molecular weight,

high viscosity products have been produced.

It is highly desirable to have low molecular weight copolymers available to the art. It is particularly desirable that such products be prepared by a low cost bulk polymerization technique which is readily controlled and which, when repeated, gives low molecular weight products in a predictable and narrow range.

Accordingly, it is an object of this invention to provide a novel polymerization process for preparing low molecular weight polyanhydrides derived from maleic anhydricle and vinyl hydrocarbons.

It is a further object of this invention to provide a process wherein more consistent and specific properties of the polyanhydrides are obtained.

Still another object is to provide novel, low molecular weight polyanhydrides possessing a higher degree of reactivity, lower softening points and higher molar ratios of maleic monomer.

A further object of the present invention is to provide novel epoxy compositions containing said polyanhydrides which exhibit improved properties.

These and other objects will be apparent from the description of the invention which follows.

POLYANHYDRIDES AND PREPARATION THEREOF The above and related objects are attained by a novel process in which the maleic monomer is heated, preferably under an inert atmosphere, to a temperature within the range of about 160 to about 200 C. and the vinyl monomer is slowly added thereto, with agitation, at a rate which allows for the necessary control of the heat of reaction, the reaction temperature being maintained within said range until essentially all of the maleic monomer and alkyl styrene have polymerized, said reaction being conducted in the absence of solvent and catalyst to yield a polyanhydride having a molecular weight below about 1,000, generally within the range of about 200 to about 950 and especially about 300 to 450, containing maleic monomer to vinyl monomer in a ratio greater than 1 to 1.

The novel polyanhydrides provided by the instant process possess unusually attractive properties which render them particularly suitable as hardeners in epoxy molding compositions and offer several advantages as hardeners over conventional mono and dianhydrides when employed in such compositions as illustrated further hereinbelow. The novel polyanhydrides have low softening points, e.g. 111-156 C., and offer better processibility as components of various formulated epoxy compositions suitable for use as epoxy laminating resins, epoxy potting resins, epoxy coating resins and other miscellaneous applications well known to this art. Such epoxy compositions including those containing fillers show rapid cure even with epoxy resins having relatively high epoxy equivalent weight and result in cured products having high heat distortion temperatures (HDT) and excellent electrical and shelf life properties. These improvements are mainly attributed to the higher molar porportion of maleic anhydride which allows for a higher degree of reactivity which in turn gives rise to faster cure, high HDT, etc. in epoxy resin-containing compositions.

The novel process also possesses certain advantages over prior procedures. It is a bulk polymerization allowing virtually percent utilization of kettle capacity as compared to conventional solvent processes which utilize only 10 to 50 percent of kettle capacity for actual product produced. Secondly, elaborate and expensive equipment is not required since any conventional polyester reaction kettle can be employed with satisfactory results. Additionally, vacuum stripping of the product is not required and free vinyl monomer in Patented May 8, 1973.

'heat of reaction. These factors are obtained by adding the maleic anhydride initially, adding the vinyl monomer at a slow rate and effecting the reaction at an elevated temperature. It is believed that the slow addition of the vinyl monomer keeps the amount of free monomer so low that the heat of reaction is easily dissipated and thereby prevents the normally run-away reaction and allows production of low molecular weight products. Moreover, it is believed that the high temperature at which the reaction is initiated is of critical importance.

It is believed that at temperatures lower than 160 C., initiation of the reaction is so slow as to permit a build- 'up of monomer which, once the reactio nis initiated,

allows for a run-away, uncontrolled reaction. To the contrary, at temperatures of from about 160 C. to 200 C., the latter temperature being the reflux temperature .of maleic anhydride, reaction is spontaneous and this condition, coupled with the slow addition of vinyl monomer permits control of the heat and rate of reaction.

The process of the invention is generally adaptable to the copolymerization of alkyl substituted styrenes including those containing additional substituents inert to the reaction. In general, such alkyl styrenes are of the formula:

wherein R is hydrogen or alkyl containing 1 to 4 carbon atoms with the proviso that when X and X are hydrogen, R is alkyl; X and X are hydrogen, halogen such as chloro, bromo, and iodo; alkoxy alkyl and haloalkyl wherein the alkyl groups contain from 1 to 4 carbon atoms; acetyl, monocyclic aryl such as phenyl, tolyl, xylyl; aralkyl such as benzyl, phenethyl, etc. or X and X together with the benzene nucleus may form a fused ring. Such alkyl styrenes include a-methylstyrene, isopropyl styrene, vinyl toluene, tertiary butyl styrene, vinyl xylene, 2,4-dimethyl styrene, 2-methyl-4-chlorostyrene, vinyl naphthalene, 2-methyl-4-benzyl styrene, and mixtures thereof.

It has been found that the conventional polymerization catalysts and molecular weight regulators heretofore believed to be essential to promote free radical initiation are not necessary in the practice of the instant invention. It has been previously believed that the molecular Weight of the products would be significantly lowered when using high catalyst concentrations. To the contrary and unexpectedly, in the present invention, such catalysts have little or no effect and offer no advantage. Similarly, molecular weight regulators are not required to produce the low molecular weight products of the invention although they may be employed in certain instances ifdesired. Such molecular weight regulators include mercaptans, for example, isooctyl mercaptan, octadecyl mercaptan, lauryl mercaptan, etc. nitrostyrene, chlorohydrocarbons for example chlorobenzene, dichlorobenzene, chloroxylene, etc. and other compounds well known in the art for this purpose.

. It is a distinction of this invention that-the preferred vinyl monomer, a-methyl styrene, appears to function as a molecular weight regulator in the instant reaction. This is illustrated by preparation'of extremely low molec- 4 ular weight polyanhydride copolymers, e.g. 300-450 M.W., when reacting a-methyl styrene and maleic anhydride. The molecular weights of copolymers are slight-. ly higher when employing alkyl styrenes other than amethyl styrene. For example, tertiary butyl styrene-maleic anhydride copolymer has a M.W. of about 638 while the terpolymer with a-methyl styrene has a molecular weight of about 550. Thus, the preferred polyanhydrides of the invention will be copolymers of a-methyl styrene and maleic anhydride and terpolymers of a-methyl styrene, other alkyl styrenes, for example, tertiary butyl styrene and maleic anhydride. Alternatively, copolymers of alkyl styrenes other than u-methyl styrene but exhibiting the lowest molecular weight may also be prepared by employing molecular weight regulators such as lauryl mercaptan as illustrated further hereinbelow. Use of the latter molecular weight regulator is not preferred, however, since it imparts an unpleasant odor to the final product. It is a further distinction of this invention that while copolymers, terpolymers, etc. of the alkyl styrenes with maleic compounds may be prepared having low molecular weights, styrene, which is normally the preferred reactant in other procedures, is not operable unless reacted in conjunction with one of the alkyl styrenes of the invention. As will be illustrated further hereinbelow, attempts to produce styrene-maleic anhydride copolymers in the absence of alkyl styrene by the present process resulted in run-away reactions with large amounts of polyestyrene forming over the sides of the reactor, the products beingextremely viscous and having high molecular weights.

The maleic compounds copolymerized with the above vinyl monomers are, in general, compounds which have one carboxyl group attached to each carbon atom of an olefinic group, i.e., wherein two carbon atoms are joined by a double bond. The remaining valences of each of the double bonded carbon atoms are generally satisfied by organic groupings or inorganic groupings which are essentially inert in the principal copolymerization reaction. Thus, the maleic compound will have only one olefinic linkage. Illustrative of such maleic compounds are materials defined by the following general formula wherein R and R can be hydrogen, halogen such as chloro, bromo and iodo; aryl such as phenyl, xylyl, tolyl, etc.; aralkyl such as benzyl, phenetyl, etc., or alkyl, the alkyl groups containing 1 to 10 carbon atoms; or cycloalkyl such as cyclopentyl, cyclohexyl, etc.; X and Y can be OH, I, or X and Y together is 0. Typical examples of such compounds include maleic anhydride, methyl maleic anhydride and materials which rearrange thereto during the reaction such as itaconic anhydride; propyl maleic anhydride, 1,2-diethyl maleic anhydride, phenyl maleic anhydride, cyclohexyl maleic anhydride, benzyl maleic anhydride, chloromaleic anhydride, and maleic acid. Maleic anhydride is especially preferred.

The maleic monomer and the vinyl monomer will be employed in molar ratios greater than 1.0 mole maleic monomer to 1.0 mole of vinyl monomer, preferably in the range of 1.1 to 1.0 to 2.0 to 1.0.

The processing techniques of the invention are subject to variation. It has been found that all of the maleic monomer may be added .to the kettle and heated to the prescribed temperature or a majorportion may be added, the remainder being added after all ofthe vinyl monomer has been added. In the latter procedure, the final addition of a small amount of maleic monomer aids in keeping the amount of free vinyl monomer in the product to a minimum. It is not desirable to employ reverse addition, e.g. to add vinyl monomer to the kettle followed by slow'addition of maleic monomer since such a procedure results in highly viscous copolymers of molecular weights outside the desired range which are not suitable for use in epoxy molding compounds. Since under optimum conditions, there is less than 1.0% unreacted vinyl monomer, the products are recovered by merely pouring into containers. Recovery, where needed, however, may be easily accomplished by vacuum stripping unreacted material by conventional means.

The following examples are set forth to illustrate more clearly the principle and practice of this invention. Where parts or quantities are set forth, they are parts or quantities by weight.

EXAMPLES 1 TO 7 1960 parts moles) of maleic anhydride were charged to a polymerization kettle after the kettle was 20 flushed free of air with nitrogen. The charge of maleic anhydride was heated to 180 C. with stirring after which 1770 parts (15 moles) of alpha-methyl styrene were added over a 3 /2 hour period. After said addition was complete, the temperature was raised to 200 C. over minutes. 5 250 parts (2.53 moles) of additional maleic anhydride was added to the reaction zone and heated to 200 to 210 C. for one hour after which the liquid was dropped into containers. There were recovered a solid polymer having a Ring and Ball softening point of 111 C., a Gardner- 3 Holdtviscosity of UV (40% resin in tetrachloroethane),

a molecular weight of 350 and anhydride equivalent III weight of 177.

The procedure of Example 1 was repeated except the reactants and conditions were varied as indicated with the results reported in Examples 1 to 7 in Table I which follows. In Example 2, the procedure 'was the same except that all of the maleic anhydride was added initially.

EXAMPLES 3 TO 10 40 For purposes of comparison, several experiments were run and are reported in Table I also.

In comparative Example 8, the procedure of Example 1 is repeated except that styrene is substituted resulting in an uncontrollable reaction with high formation of polym styrenes.

In comparative Example 9, a 1:1 styrene-maleic anhydride copolymer is prepared by solvent process as follows:

Part A:

2400 grams xylene N Part B:

2.4 moles maleic anhydride 2.4 moles styrene 1 /2% tertiary butyl perbenzoate catalyst 320 grams xylene Part A is charged to the kettle and heated to 95100 C. Part B is dissolved together and added to the reaction vessel over a 2 hour period after which it is maintained in the vessel for 2 hours at 95100 C., cooled to 30 C. and filtered. The product starts to precipitate after 30 minutes and is recovered as a finely divided precipitate. The product could not be melted for softening point determination as it blackened or carbonized as the temperature increased. The softening point-was thereby indicated to be well above 200 C.

In comparative Example 10, a commercially available 1:1 styrene-maleic copolymer, commercially available as SMA 1000-A, Arco Chemical Company, is listed and employed in subsequent experiments hereinbelow.

In Table I, abbreviations where they appear have the following meanings: Ix MS is alpha methyl styrene; S is styrene; VT is vinyl toluene; TBS is tertiary butyl styrene; TCE is tetrachloroethane; DMF is dimethyl formamide; and TBPB is tertiary butyl perbenzoate catalyst.

W, 60% resin DMF Y, 383 7565111 l l I I l I I I I I I I I I I I I l l I-I I l I l I I I I I I I I I l I I I l l I I I-( I I I I I I I I I I I I "I O I I I l l TBS, 7.2.

mercaptan.

U, 40% resin vinyl monomerjmalcie monomer-.. 1.0/1.5 1/2 1.0/l.33 1.0 1.125--- 1.0/1.33. hours 3 2 0...--. 180 -V, 40% resin TOE. Molecular weight.... 350-.--

I no

I I l I H I I m I I l 1 l a i 00 E I I o: H

I o cu Example, 1

Maleie anhydride (moles):

Vinyl monomer (moles) aMS, 15.0- aMS, 6 VT, 7.2 Ratio of reactants Catalyst- Addition time,

Reaction temperature,

1 Reaction stopped after of styrene added. Large amounts of polystyrenes over sides and top of reactorn. 1 Would not me t for softening point; carbonized before softening.

Softening point, C 111 123. Remarks Polyanhydride prepolymer In a preferred embodiment of this invention, low melting, economical epoxy-hardener prepolymers are provided which have extremely low Ring and Ball softening points and provide greater ease of processing with additional epoxy resin and other components of epoxy composition. For example, in the preparation of epoxy molding compounds, to optimize blending of the hardener with the resin of the molding compound when the polyanhydridies per se are employed, the polyanhydrides are first ball milled to-a fine powder prior to blending and processing. This step is not necessary when employing the polyanhydride prepolymer. Additionally, this embodiment of the invention permits ready use of liquid epoxy resins of low epoxy equivalent weight and high reactivity.

The preparation of the prepolymer is simple in that the epoxy resin is simply added to the polyanhydride hardener product while it is still in the reaction kettle. The prepolymer-s are characterized by ,good stability and range from viscous liquids to materials which exhibit Ring and Ball softening points below 100 C., generally within the range of about 40 to 95 C.

A variety of low equivalent weight epoxy resins can be reacted with the polyanhydrides to form the prepolymer herein. They include glygcidyl polyethers of polyhydric alcohols and polyhydric phenols well known in the art, for example, diglycidyl ethers of Bisphenol A commercially available as 'Epon resins. Other suitable resins include polyglycidyl ethers of phenol-formaldehyde novolacs and cresol-formaldehyde novolacs, cycloaliphatic epoxy resins, etc. In general, suitable epoxy resins will be characterized as having an epoxy equivalent weight within the range of about 75 to about 500.

The prepolymers are prepared by adding from about 0.1 to about 1.3 equivalents of epoxy per anhydride equivalent weight.

This aspect of the invention will be'better understood from the example which follows:

EXAMPLE '11 Following the procedure of Example 2 and employing the reactants thereof, the reaction is allowed to cool to 155 C. A cpmmercially available diglycidyl ether of Bisphenol A, having a molecular Weight of 380-400 (at 45 to 50 C.) equal to 54 percent of the charge in the kettle is added over 5 to minutes with stirring. The temperature drops to .about 115 C. and is held there for 30 minutes after which the product is dropped into containers. The product is a prepolymer containing 65% polyanhydride/ 35 e'poxy, has a Ring and Ball Softening point of 81 to-85 C. and a Gardner-Holdt viscosity (40% resin in tetrachloroethane) of D-G.

When the polyanhydride of Example 1 is substituted in the above experiment, a prepolymer is received of comparable viscosity and having a softening point within the range of 69 to 76 C.

Epoxy molding compounds Epoxy molding compounds employing the polyanhydrides or prepolymers of this invention have improved physical and molding properties especially in high temperature dry and wet electrical properties of the molded pieces, in shelf life of the molding compounds and in release during molding.

Suitable epoxy molding compounds may be prepared by conventional techniques, for example, by dry blending the components in a suitable mixer followed by suitable processing, for'example, fusion on a heated two roll mill. Process temperatures will vary according to the resin and hardener types employed but are generally within the range of about 75 F. to 250 F. The fused product is then cooled and granulated in a suitable grinder such as a Fitzpatrick mill. v

group. The polyepoxides may be saturated or unsaturated, aliphatic, cycloaliphatic, heterocyclic, aromatic and may be substituted if desired with substituents such as chlorine, hydroxyl, ether radicals and the like.

Various examples of polyepoxides that may be used I in the process of the invention are given in US. 2,633,458 and it is to be understood that so much of the disclosure of the patent relative to examples of polyepoxides is incorporated by reference into this specification.

Other examples include the epoxidized esters of the polyethylenically unsaturated monocarboxylic acids such as epoxidized linseed, soybean, perilla, oiticia, tung, walnut and dehydrated castor oil, methyl linoleate, butyl linoleate, ethyl 9,'-l2-octadecadienoate, butyl 9,12,15-octadecatrienoate, butyl eleostearate, monoglycerides of tung oil fatty acids, monoglycerides of soybean oil, sunflower, rapeseed, hempseed, sardine, cottonseed oil, and the like.

Another group of the epoxy-containing materials used in the process of the invention include the epoxidized esters of unsaturated monohydric alcohols and polycarboxylic acids, such as, for example,

Another group of the epoxy-containing materials includes those epoxidized esters of unsaturated alcohols and unsaturated carboxylic acids, such as 2,3-epoxybuytl 3,4-epoxypentanoate, 3,4-epoxyhexyl 3,4-epoxypentanoate, 3,4-epoxycyclohexyl, 4,5-epoxyoctanoate, 2,3-epoxycyclohexylmethyl epoxycyclohexane c'arboxylate.

Still another group of the epoxy-containing materials included epoxidized derivatives of polyethylenically unsaturated polycarboxylic acids such as, for example,

dimethyl 8,9,12,13-diepoxyeicosanedioate,

dibutyl 7,8,1 1,1Z-diepoxyoctadecanedioate,

dioctyl 10,1 1-diethyl-8,9,12,13-diepoxy-eiconsanedioate,

dihexyl 6,7, 10, l 1-diepoxyhexadecanedioate,

didecyl 9-epoxy-ethyl-10g1l-epoxyoctadecanedioate,

dibutyl 3-butyl-3,4,5,6-diepoxycyclohexane-1,2-dicarboxylate,

dicyclohexyl 3,4,5,6-diepoxycyclohexane-1,2-dicarboxylate,

dibenzyl l,2,4,5-diepoxycyclohexane-1,2-dicarboxylate and diethyl 5,6,10,1l-diepoxyoctadecyl succinate.

Still another group comprises the epoxidized polyesters obtained by reacting an unsaturated polyhydric alcohol and/or unsaturated polycarboxylic acid or anhydride groups, such as, for example, the polyester obtained by reacting 8,9,l2,l3-eicosanedienedioic acid with ethylene glycol, the polyester obtained by reacting diethylene glycol with 2-cyclohexene-1,4-dicarboxylic acid and the like, and mixtures thereof.

Still another group comprises the epoxidized polyethylenically unsaturated hydrocarbons, such as epoxidized 2,2 l bis((2 cyclohexenyl) propane, epoxidized vinyl cyclohexene and epoxidized dimer of cyclopentadiene.

Another group comprises the epoxidized polymers and copolymers of diolefins, such as butadiene. Examples of this include, among other, butadiene-acrylonitrile copolymers (Hycar rubbers), butadiene-styrene copolymers and the like.

Another group comprises the glycidyl containing nitrogen compounds, such as diglycidyl aniline and diand triglycidylamine.

The polyepoxides that are particularly preferred for use in the compositions of the invention are the glycidyl ethers and particularly the glycidyl ethers of polyhydric phenols and polyhydric alcohols. The glycidyl ethers of polyhydric phenols are obtained by reacting epichlorohydrin with the desired polyhydric phenol in the presence of alkali.

Polyether A and Polyether B described in the abovenoted US. 2,633,458 are good examples of polyepoxides of this type. Other examples include the polyglycidyl ether of l,1,2,2-tetrakis(4-hydroxyphenol)ethane (epoxy value of 0.45 eq./ 100 g. and melting point 85 C.), polyglycidyl ether of 1,1,5,5-tetrakis(hydroxyphenol)pentane Fillers may be employed in the instant polyepoxide compositions in varying amounts to convey special properties thereto where desired. Such fillers suitable for use include among others, silica, mica, calcium carbonate, fiber glass, talc, asbestos, alumina, zinc oxide, cellulose and mixtures thereof. The amount of filler added to the polyepoxide composition may vary over a wide range. In general, amounts ranging from about 500 to parts by weight per 100 parts by weight of polyepoxide component are preferred.

The following examples are given to illustrate epoxy molding compounds of this invention.

EXAMPLES 12 TO 20 Epoxy molding compounds are prepared employing 22.9 parts by weight of diglycidyl ether of bisphenol A, having an equivalent weight of 488, 7.1 parts by weight polyanhydride hardener, 0.2 part by weight tn's(dimethylaminomethyl)phenol as catalyst, 0.2 part by weight mold lubricant, and 67.8 parts by weight silica filler. The ingredients were dry blended followed by roll milling at 140-150 F. after which the fused product was cooled and granulated in a Fitzpatrick mill. The resulting molding compounds were evaluated for flow properties and shelf life and were then transfer molded at 300 F. for five minutes, postcured for 2 hours, at 135 C. Molded specimens were tested for mechanical and electrical properties.

The results are reported in Table II which follows in which the same procedure was employed in each example except that various hardeners were substituted, as indicated. In all instances, the proportions of epoxy resin plus hardener equaled 30 weight percent of the composition and the A/E ratio was maintained at 0.85.

TABLE II Retention of flow at 100 F. (shelf life) Initial EMMI EMMI flow flow and gel 7 days 17 days Hot Shore D hardness alter Hard- Maleie/ and gel, 300 F. time at 350 F. cure at 325 F.

ener, Hardener type and vinyl Per- Per- Example percent example number ratio In. See. In. See. In. cent In. cent 2 min. 3 min. 4 min. 5 min. 1

7. 1 aMS/MA of EX. 1 1. 5 27. 5 43 37 16 29 78 30 81 60 72 73 75 7. 5 VT/MA of Ex. 3. 1. 33 17. 5 41 27 13 20 74 20 74 72 72 74 75 8.1 TBS/MA of Ex. 5 1. 33 7.0 36 11 7 10. 5 96 10. 5 96 70 74 77 77 7. 9 VT/ozMS/MA of Ex 6 1. 125 11 16 14 15 12.5 89 10. 5 75 76 77 77 77 8.6 TBS/aMS/MA of Ex 1. 125 14 33 16 13 14 88 13 81 70 76 79 79 6. 4 aMS/MA of EX. 2 2. 0 20 36 27. 5 13 26 95 22. 5 82 77 80 80 80 7.4 S/aMS/MA of Ex. 4 1. 125 14.5 21 20 10 16. 5 83 15 75 70 73 75 77 8.0 S/MA of Ex. 9 1. 0 5 8.5 S/MA of Ex. 10 1.0

1 No flow, no cure. 2 N 0 cure.

(epoxy value of 0.514 eq./ 100 g.) and the like and mixtures thereof. Other examples include the glycidated novolacs obtained by reacting epichlorohydrin with novolac resins obtained by condensation of aldehydes with polyhydric phenols.

The polyepoxide and polyanhydride hardeners are employed in proportions to provide at least 0.5 equivalent of anhydride. Generally, the proportions will range from 0.5 to 2.0 anhydride group per epoxy group and preferably from about 0.7 to 1.1.

Various catalysts may be employed to promote the curing of said compositions and are well known within this art. Such catalysts include basic and acidic catalysts such as the metal halide Lewis acids, e.g. boron trifluoride, stannic chloride, zinc chloride and the like; the amines, e.g. alpha-methyl benzyl-dimethylamine, dimethylethylamine, dimethylaminoethylphenol, 2,4,6 tris(dimethylaminoethyl) phenol, triethylamine and the like. Such compounds are employed in the amounts conventional in the art, e.g. from about 0.1 to 5.0 percent by weight of the binder system.

Various other ingredients may be mixed with the polyepoxide composition including pigments, dyes, mold lubricants and the like.

Table II is an evaluation of flow, cure, and shelf life properties of the instant molding compositions. EMMI flow via EMMI Spiral Flow Specification EMMI I-66 in-' volves the transfer molding of the material from a pot through a sprue into an open ended spiral cavity under controlled conditions of temperature and pressure. The Gel Time reported in Table II was determined by the use of a ram follower device in conjunction with the EMMI Flow mold.

The first observation readily apparent from the table is that both compounds based on solvent polymerized styrene maleic anhydride at a 1:1 ratio did not cure and had little or no flow even at 350 F., a fact probably attributable to the high softening points of these compounds which prevent adequate fusion of the hardener with the resin which is required for adequate cure and flow. All of the products of the present invention possess good flow, cure and hardness properties and very good shelf life, an advantage over many exisitng epoxy molding compounds.

The epoxy molding compounds of the above examples were similarly evaluated for other properties such as heat distortion temperatures (HDT), flexural strength and ele'c- 3,732,332 -1 l 1 2 tricals,- the results of which are reported in Table III. Wt. percent Moisture absorption data after 16 hours at 15 p.s.i.g. Epoxy resin ig y i y r of sphenol A) molecsteam was determined and reported below. Dielectric conlllflf Weight 1000 stants (DK) and dissipation factors (DF) were deterq I III mined on these materials at 25 C., 175 C., and at 25 C. 5 figg g fi me acce or after exposing the test piece for 16 hours 1n a pressure Finer 700 cooker at '15 p.s.1.g. steam. Dye 0.95

' TABLE III HDT, C. Percent alter cure at water 325 F. absorpfor 5 mm.; tion, 16 Electricals v post-cure Flexural Flexural hrs., 2 hrs. at strength, modulus, p.s.i.g. DK, 60 DK, DF, 60 DF. Example Hardner type 175 0. psi. p.s.i. l0 steam cycles 1 kc. cycles 1 kc 12A 'aMS/MA of Ex. 1 153 16,037 1. 78 74 e 4.19 I 3. 99 I 0094 .0089 b 5. 21 b 4. 94 b 0390 b 0252 c 7. a .300 13A VT/MA of Ex. 3 145 17, 646 1. 83 84 l 4.13 a 3. 97 I 0085 I 0075 5.18 b 4. 89 b 0390 b 0262 I 7.20 ase .300 124 14A TBS/MA of Ex. 5 148 14, 246 l. 73 81 l 4. 16 l 4. 08 0080 l 0086 5.13 4.86 .0398 .0239 11.54 6.23 .742 .254 um VT/uMS/MA or Ex. 0 105 10. 200 1.87 .04 4.10 4.11 0030 a .0086 5. 27 5.03 .0427 .0271 i -6.13 5.29 .154 .0693 16A TBS/aMS/MA of Ex. 7 167 15, 012 2.02 76 4,11 4, 05 a 0036 a 0076 506 4.80 .0354 .0224 7 8.07 5.50 .421 L149 17A MS/MA of EX. 2 131 14,300 1. 75 .73 -4.23 4. 11 0009 .0061 v h 5. 01 b 4. 82 b 0291 0160 8. 49 510 13A z/ Ms/MA of E 4 141 12, 905 1. 85 96 I 4. 22 a 4.16 I 0085 l 0078 5.37 5.09 .0412 .0264 "7.00 5.70 ".202 M0080 =25 C. h =175 C. =25 C. after exposure to 15 p.s.i.g. steam for 16 hrs.

EXAMPLE 21 v v The compounds were processed and cured as in Ex- Epoxy molding compounds are prepared employing 8.0 ample 12. In the table, the abbreviations have the folparts by weight of epoxy resin, a diglycidyl ether of Bislowing meanings: DF is dissipation factor; BROB means phenol A having a molecular weight of 460-560, to which the value was so high it could not be measured by the was added 13.0 parts by weight of prepolymer hardener test employed; Commercial Epoxy Molding Compounds described in Example '11, 0.14 part by weight of tertiary A, B and C are commercially available epoxy systems amine catalyst, 0.50 part by weight mold lubricant and containing diglycidyl ethers of bisphenol A as resin, silica 78.3 parts by weight silica filler. 40 fillers and monofunctional anhydride hardeners.

TABLE IV Elcctricals, dry Electricals, wet

l5 p.s.i.g. steam Shelf life, 100 F DF cycles 16 hours EMMI flow .A/E HDI, Weight 3 7 Example Hardener or epoxy system ratio 0. 25 0. 175 0. gain DF. Initial days days 22 aMS/MA 77 135 .0065 100 80 050 30 25 22 23.-- Trlmellitic anhydride 1. 0 121 90 24... Phthalic anh dride 1.0 108 27 25 'Ietrahydrop thalic anhydride .90 Q7 ,42 26 Hexahydrophthalic anhdyrlde 90 97 13 27 Succinic anhydride 1 0 96 90 28 Benzophenone tetracarboxylie dianhydride 1 0 172 70 29 Commercial epoxy molding compound A. 0 Commercial epoxy molding compound B. 97 1 Commercial epoxy molding compound 0 112 j The epoxy molding compound was evaluated for a It will be obvious from Table IV, that the molding comnumber of molded properties the results of which are pounds of the invention are superior in all physical propreported below. erties tested to those derived from conventional monoanhydrides. Comparison to a commercial dianhydride g zifi ss gg ggg fi 20 60 hardener molding compound (Example 28) shows that Electrical g f gf ig f 'g at: compounds based on the novel anhydride hardeners are 60 Cycles, D07 far superior 1n a number of the important properties 60 Cycles C. 045 such as shelf life and high temperature and wet electricals. Electrical properties, wet (after 15 p.s.i.g. steam The COmPQUHdS based on the novel anhydride hardener for16hourS). p also exhi bited superior mold release after exposure to Weight gain, percent 60 humld agmg condltlons- Dissipation factor at 60 cycles .025 EXAMPLES 32 To 36 For'comparative purposes, the instant molding compounds were compared with various monoanhydride and The following examples are given to illustrate molding dianhydride cured epoxy molding compounds and with compounds derived from other types of epoxy resins preseveral commercially available anhydride epoxy compared by the procedure of Example 12. In the table, TBS- pounds and the results reported in Table IV. aMS-MA is a polyanhydride of tertiarybutyl styrene-al- The formulation was as follows with variations as inpha-methyl styrene and maleic anhydride described in dicated in the following table. Example 7; DGEBA epoxy resins are coinmerciallyavailable resins of the diglycidyl ether of Bisphenol A type; novolac epoxy resin is a polyglycidyl ether of o-cresol formaldehyde novolac; and cycloaliphatic epoxy resins are low viscosity cycloaliphatic resins, 3,4-epoxycyclohexyl- D GEBA epoxy M.W. ,000- Novolac epoxy M.W. 1,100 Oycloaliphat-ic epoxy M.W. 426 12. Oycloallphatic epoxy M.W. 280;. TBS-aMS-MA.-.-. Carbon black Coupling agent.. Fiberglass ZnO 330 F., Shelf life, 100 F.:

Initial .0 After pressure pct (16 (13118., p.s.l.g.

steam) tested at 25 60 050 353 Dielectric constant, 60 cycles:

25 4. 4. 36 4.18 4.06 4. 06 175 C 5.20 5.39 4.81 4. 97 4.85 After pressure pot (16 hrs., 15 p.s.i.g.

steam) tested at C 6. 22 5. 4. 78 7. 61 5. 55

While the above epoxy systems have been described as particularly suitable for use as molding compounds and this use is a preferred embodiment herein, it will be obvious to those skilled in the art that they are equally suitable for other uses, for example, in fusion coating and solvent system coating laminating applications; fluid bed and electrostatic coating applications, etc. They are further useful in such applications as bonding of thermal insulation wherein thermal stability affords an excellent property.

The polyanhydrides can likewise be employed as'coreactants with other anhydrides, as flow promoters and elevated temperature modifiers for thermoplastics, etc.

We claim:

1. A thermosettable composition comprising a mixture of (A) an epoxide compound having at least two 1,2-epoxide groups and (B) as hardener therefor a number selected from the group consisting of (,1) a polyanhydride having a molecular weight below about 1,000 and a softening point of 111 C. to 156 C., said polyanhydride being the reaction product of the mass polymerization, in the absence of polymerization catalyst, of a maleic monomer and at least one alkyl styrene monomer in molar ratios of maleic monomer to alkyl styrene greater than 1 to 1 and (2) prepolymers of said polyanhydrides with an epoxide compound having more than one 1,2-epoxy group and an epoxide equivalent of 75 to 500, said epoxide being present in an amount sufficient to provide from about 0.5 to 2.0 equivalents of epoxy per anhydride equivalent weight.

2. A composition as claimed in claim 1 wherein said hardener is a polyanhydride.

3. A composition as claimed in claim 1 wherein said hardener is a polyanhydride-epoxy prepolymer.

4. A composition as claimed in claim 2 wherein said polyanhydride is derived from maleic anhydride and alphamethyl styrene.

5. A composition as claimed in claim 2 wherein said polyanhydride is derived from maleic anhydride and tertiary butyl styrene.

6. A composition as claimed in claim 2 wherein said polyanhydride is derived from maleic anhydride and a mixture of alpha methyl styrene and tertiary butyl styrene.

7. A composition as claimed in claim 2 wherein said components (A) and (B) are present in quantities sufficient to provide an anhydride to epoxy ratio within the range of 0.5 to 1.2.

8. The cured resin product produced by heat curing a composition of claim 1.

9. The cured resin product produced by heat curing a composition of claim 2.

10. The cured resin product produced by heat curing a composition of claim 3.

11. The cured resin product produced by heat curing a composition of claim 4.

12. The cured resin product produced by heat curing a composition of claim 6.

13. An epoxy molding compound which comprises -(A) an epoxide compound having at least two 1,2 epoxide groups, (B) as hardener therefor a member selected from the group consisting of (1) a polyanhydride having a molecular weight below about 1,000 and a softening point of 111 C. to 156 C., said polyanhydride being the reaction product of the mass polymerization, in the absence of polymerization catalyst, of a maleic monomer and at least one alkyl styrene monomer in molar ratios of maleic monomer to alkyl styrene greater than 1 to 1 and (2) prepolymers of said polyanhydrides with an epoxide compound having more than one 1,2-epoxy group and an epoxide equivalent of to 500, said epoxide being present in an amount sufiicient to provide from about 0.1 to 1.3 equivalents of epoxy per anhydride equivalent weight, and (C) a catalyst to promote the curing thereof.

14. An epoxy molding compound as claimed in claim 13 wherein said hardener is a polyanhydride derived from maleic anhydride and alpha methyl styrene.

15. An epoxy molding compound as claimed in claim 13 wherein said hardener is a polyanhydride derived from maleic anhydride and tertiary butyl styrene.

16. An epoxy molding compound as claimed in claim 13 wherein said hardener is a polyanhydride derived from a mixture of alpha methyl styrene and tertiary butyl styrene.

References Cited UNITED STATES PATENTS 7/1969 Heilman 26078.4 E P 9/1966 Widmer et al 26047 E A US. Cl. X.R.

117-145, 161 ZB; 161-184, 249; 2602 EA, 17.2, 17.4 CL, 18 PF, 37 EP, 47 EA, 59, 75 EP, 78.4 EP, 78.5 B B, 836

g gge UNITED STATES PATENT semen CER'llFlCATE 0F CRECTHN Patent No. 3,732,332 Dated May 8 1973 Invent0r(s) Omer' E. Curtis!\ Jrc Q et a1 It is certified that error appears in the abQVe-ddentified patent and that said Letters Patent are hereby corrected as shown below:

"'i Column 3, line 2 "reactio his" should read reaction is Column 4, line 57 "I," should be deletede Column 5, line 31, "Holdtviscosity" should read Holdt viscosity Column 6, in the Table, under Example 9 "180" should read 185 Column 10, line 59, after EMMI, "Spiral" should be inserted.

line 71, "existng" should read existing Column 13, line 2, "@017", second occurrence, should read line 48, "num-" should read mem- I Signed and sealed this 12th day of February 1974.

(SEAL) Attest: i

EDWARD M. FLETCHER JR 7 G. attesting Officer MARSFIALL DANN Commissioner" of Patents 

